The treatment of patients with congenital or acquired heart and lung disease is often uncertain because of alterations in the pulmonary circulation which are poorly understood at this time. The objective of this research is to study the effects of high and critically low blood flow, sepsis and left atrial obstruction in the canine pulmonary circulation using fully computerized analysis of pulsatile data. These techniques have been validated and are expected to be valuable in the study of the models of disease listed above and the effects of therapy such as drug administration and mechanical ventilation. BIBLIOGRAPHIC REFERENCES: DeVries, W.C. and Anderson, R.W.: Physiologic and pathologic responses of the pulmonary circulation to high flow shunts. Surgical Forum 26: 208, 1975. Hammon, J.W., Jr., Rankin, J.S., Arentzen, C.E., Anderson, P.A.W. and Anderson, R.W.: The force-frequency relationship in the intact canine right ventricle. Circulation 52 (Sup II): 765, 1975.